IRRIGATION DRAINAGE DESIGN AND MANAGEMENT MODEL - DEVELOPMENT

This paper introduces a model for the design and management of conjunctive irrigation and drainage systems. The mathematical model is based on the numerical implementation of a quasi-three-dimensional finite-difference model, which solves the Richards equation and the advective-dispersive transport equation for one-dimensional vertical flow and salt transport in the variably saturated zone above the water table; and it also solves the depth-averaged Boussinesq equation and two-dimensional advective-dispersive transport equation for areal flow and salt transport in the fully saturated zone below the water table. The model is fully interactive and is provided with a graphic user interface (GVI). It can be used to estimate the growth response of a crop to its soil-water-air-solute subsurface environment as influenced by drainage design and management practices such as irrigation scheduling, leaching, and cropping patterns. An illustrative example is included to demonstrate the capabilities of the model as a design and management tool in irrigation and drainage systems.